How to convert grease pencil thick controur into 2d-mesh?
My solution has been to create a path with Krita then drag the png into Blender and &quot;trace image to grease pencil&quot;. Then when you convert to polygon curve you get the result you are after.
It is possible to do it entirely within Blender by having Blender create the png from a grease pencil though it seems a little complicated.  Draw your shape with the grease pencil. Then give it a texture which defaults to black. Then change the world colour to white with no alpha in the shader editor.  Then add an opacity modifier to your grease pencil stroke and  in the modifer options set uniform opacity and select your material in the material dropdown.  You might need to add your layer in the layer dropdown as well.  Then, render your grease pencil as an image and save it as a jpeg.  You don't need your grease pencil stroke anymore.  Now, create an image empty and load your jpeg from the tab for empties in the properties section (You should be able to just drag the image into the viewport instead but I found this didn't always work).  This will give you your shape with a nice white background.  Now &quot;trace image to grease pencil&quot;. Turn off visibility for your empty and then convert the grease pencil to polygon curve.  Remember to turn visibility off for your grease pencil at this point.